The present invention relates to carriage for mounting a recording head, and a recording apparatus or a liquid ejecting apparatus having a mechanism for adjusting the distance between the recording head and a recording medium opposed thereto.
Among large-size recording apparatus capable of recording on up to a sheet (recording medium) of a relatively large size such as the A4 to A2 size of the JIS (Japanese Industrial Standards) standard are ink jet printers. In such large-size ink jet printers, a sheet is supplied from and ejected to the front side for the following reason: unlike in small-size ink jet printers, it is difficult to supply a sheet from the back side and eject it to the front side because relatively heavy sheets need to be handled.
An ink jet printer is known in which a sheet supply tray and a sheet ejection tray are disposed on the front side. A sheet that is accommodated in the sheet supply tray is taken out by a sheet supplying roller and then fed to a platen of a recording section by transporting the sheet by a sheet feeding roller and a follower roller while holding it therebetween. Recording is performed on the sheet by ejecting ink droplets from a recording head, and the sheet is then ejected to the ejection tray by transporting it by a sheet ejecting roller and a spur roller serving as a follower roller while holding it therebetween (cf., Japanese Patent Publication No. 11-124271A).
Such an ink jet printer is equipped with a gap adjusting mechanism capable of adjusting the gap between the recording head and the sheet so that it is always kept constant even if the medium thickness is varied (cf., Japanese Patent Publication No. 2002-67428A).
In the above ink jet printer, the carriage is attached to a guide shaft extending in the primary scanning direction via thrust bearings that are attached to the carriage on the back side. A front portion of the carriage is mounted on a frame of the printer and the carriage is slid along the guide shaft and the frame by a belt mechanism. However, if the ink jet printer is of a large size, the carriage is also large and heavy and hence the resistance of sliding on the guide shaft and the frame is high, which may result in wear of the guide shaft and the frame or a bend of the guide shaft. Wear or a bend of the guide shaft or the frame lowers the accuracy of reciprocation of the carriage, which may in turn lower the recording accuracy.
In the above ink jet printer, the gap is adjusted by rotating two eccentric shafts that guide the carriage on the front side and the back side as the carriage is moved. However, since the drive force of a motor for rotating the eccentric shafts is transmitted by a gear mechanism, backlash tends to occur to possibly lower the accuracy of the gap adjustment.